(n.): Any person who is well-read, articulate, and capable of formulating intelligible positions on a wide range of topics, but which happen to be demonstrably false. Derived from "Mensa" and "retard".
(Adj): Mensatarded

Dan: Having read Marx, and Rand, and Locke, and Smith, I remain resolute in my assertion that communism is a great idea that has never been fully or properly implemented.

John: Dan, if decades of evidence to the contrary combined with the hundreds of millions of dead bodies that go with those "poor implementations" of communism are not enough to convince you otherwise, I must conclude that you are, in fact, a mensatard.